Hi
If you are in receipt of foreign income, such as an overseas pension or bank interest, you will need to report this on a self assessment tax return. If your only source of income world-wide is your UK bank interest, then a tax return is not required. Please have a look at
Check how to register for Self Assessment. If you still require a self assessment tax return, you can register onine at
Register for Self Assessment if you're not self-employed. If you are unable to register using the online service, you can print and post the form SA1, which can be found at the bottom of the screen.